Metals and Alloys Subcommittee Agenda and Minutes

Metals and Alloys Subcommittee
March 24, 2004

1. Call to Order and Introductory remarks

A guest, Pierre Villars of Materials Phases Data System (MPDS) in Switzerland, and a new M&A member, Camille Jones of NIST, were introduced

2. Adoption of 2003 minutes

Minutes were approved.

3. Board of Directors Items

Cam Hubbard reported that both motions from the previous meeting were approved by the Board of Directors. A subcommittee web page was created, and a meeting between ICDD, M&A, and MPDS editorial personnel was held in October.

4. Review of Current Set

Review of Release 2004 was completed in October.

5. Metals & Alloys Working Group Report

a. Pearson Symbol Index Review Status

Prototype assignments and Pearson Symbol Code assignments have been 85% successful. Target completion date is March 2005.

b. Common Names and Strukturbericht Symbol Index Updating

Each common name entry, points to a PDF number, which in time, may become a deleted pattern, when an improved pattern is entered into the database. As annual sets are release, an automatic method to replace deleted PDF numbers with the new numbers of the improved patterns is needed. Pete Wallace has submitted a proposal for automatic editing of these indexes to the ICDD Editorial Department for their consideration.

c. Calculated Pattern Round Robin

Larry Calvert’s “Test Data for the Calculation of Powder Patterns for Intermetallic Phases” has been used to calculate patterns using several programs.

J.Johnson - Don’t compare to experimental patterns.
M.Bennett - Powder Cell and 2 versions of POWD available at HQ.
J.Johnson - Be careful with copyright usage of these programs.

Other Rietveld-like programs:

BGMN Joerg Bergmann
FOX Vincent Favre-Nicolin
and Radovan Cerny
FULLPROF Juan Rodriguez-Carvajal
GSAS Robert Von Dreele
JANA2000 Vaclav Petricek
MAUD L. Lutterotti  

d. Metals & Alloys Web Page

Camille Jones volunteered to be the M&A Webmaster. Doug Smith offered to help.

e. Virtual Blue Book

The VBB has been produced in Adobe format.

6. Linus Pauling File (LPF) and Powder Diffraction File (PDF) Prototype Structures

The goal is to keep M&A prototype structures consistent with those of the LPF. Toward that end, we have obtained tables from LPF that permit us to compare M&A and LPF prototype structures, and determine how to make needed changes.

LPF entries with atomic coordinates were analyzed to determine the correct prototype assignment. The analysis involved placing the structure in a standard (Parthe) unit cell, determining the atomic environment for each atom, and comparing the environments to those of possible prototype structures. LPF entries without atomic coordinates were individually evaluated by LPF editors to determine the correct prototype structure.

LPF prototypes have changed from the Pearson handbooks in different ways. Pearson used alphabetical order of the elements, while LPF arranges the elements according to electronegativity. There may be a new formula with different elements (because an older reference was found), or one old prototype is now represented by two new prototypes, or two old prototypes are now combined into one new prototype.

Pearson LPF
Ag Cl Tl I
Al2 Fe Fe6.5 Al11.5
O7 V4 Ti4 O7

The LPF has added the filled Pearson Symbol and Space Group number to the prototype name to make them unique.

Pearson LPF
Cu Cu,cF4,225
Cl Na NaCl,cF8,225
Cr3 Si Cr3Si,cP8,223
B Fe FeB,oP8,62

The ICDD relational database can have several fields for prototypes, Pearson symbols, crystallographic cells, and units for cell dimensions:

LPF prototype (includes Pearson Symbol and Space Group)
PDF prototype (in alphabetical order)
Classical prototype (replaced by another compound)
Pearson symbol (filled structure)
Pearson symbol code (actual structure)
Hydrogen-less symbol code (hydrogen atoms not counted)
Author’s Cell (the cell reported by the authors)
Crystal Data Cell (a standard cell used by the PDF)
Parthe’ Cell (a standard cell used by the LPF)
Reduced Cell  
Angstroms (These are used in the PDF.)
Nanometers (These are used in the LPF.)

M.Bennett - It’s difficult to assign prototype because of ambiguous SG.
C.Foris - How is triclinic handled?
Answer - Niggle reduced cell

7. Meeting adjourned

Submitted by
Acting Secretary
Jeffrey Dann

Cam Hubbard
Pierre Villars
Mike Bennett
George Havrilla
Jeffrey Dann
Harlan Clark
Thomas Ely
Pierre Ricou
Gerald Johnson
Camille Jones
Earl Ryba
Catherine Foris
Pete Wallace
Philippe Sarragin